Aniline leather is a type of leather dyed exclusively with soluble dyes without covering the surface with a topcoat paint or insoluble pigments. The resulting product retains the hide's natural surface with the 'grain', i.e. visible pores, scars etc. of the complete original animal's skin structure. For this reason, aniline leather is one of the most precious finishing in leather manufacturing: only high quality leathers result suitable for aniline finish.
Originally, the dyes used for this process were synthesized from aniline through chemical reactions. These dyes used to be called 'aniline dyes' or 'tar dyes'. In modern times, the dyes used are subject to laws and regulations in many countries, and the use of certain azo compounds is prohibited in the European Union as there are reasons to assume health risks.
Typically, leather is dyed both for aesthetic reasons and to conceal blemishes. The dye colours leather without producing the uniform surface of pigmented leather. Any visible variations on the surface of the undyed leather such as natural blemishes will remain visible.
There are different kinds of aniline leather, but the same kinds of dyes are used in the process. The dyes used are clear and transparent chemicals that allow the grain structure of the leather to be seen. These dyes show the natural texture, but do not protect the leather from damage.
Aniline leather may be referred to as full aniline or full sauvage leather to differentiate between this dye treatment and variants. Semi-aniline leather is produced through a very similar process to full-aniline, but has a thin protective top coat added to protect it from wear and staining. Pull-up aniline leather has additional oil or wax applied to the leather to give it a distressed look.